From the commonly assigned U.S. Pat. No. 4,765,406 and its German counterpart DE-A-36 12 946, it can be seen that an apparatus for generating steam can be used to supply the steam of a petroleum-bearing stratum for tertiary recovery of crude oil. The temperature increase in the oil-bearing stratum reduces the viscosity of the crude oil to make the crude oil flowable and pumpable, i.e. more mobile so that the mobilized crude oil can be extracted by pumping from the oil-bearing stratum.
For that purpose, the steam generator can, in whole or in part, be received within the cased bore hole and can have a pipe (steam delivery pipe) which extends from the steam generator within the cased bore hole to deliver the steam to the oil-bearing stratum.
Problems have been encountered heretofore with the sealing of the steam pipe with respect to the casing or wall of the bore hole since the steam is delivered under pressure to the oil-bearing stratum and when this stratum is under pressure. The unblocked mouth of the steam-delivery pipe must be sealed with respect to the bore hole space above the seal if steam pressure is to be maintained in the oil-bearing stratum.